1. Field of the Invention
This invention relates to a guidance conductor laid on a track way by which driverless vehicle is controlled to move along the track way by detecting the induction field generated by the single conductor.
2. Description of the Prior Art
A typical arrangement of conventional guidance conductors adapted for use in such a driverless vehicle may be shown in FIG. 1, wherein a track way generally designated by a reference numeral 1 is constructed in any predetermined shape as required for delivering goods from certain loading places to unloading places. The track way 1 is comprised of, in this example for the purpose of illustration, a main way 2 and two branch ways, 3, 3 extending out from the main way 2. There is formed a guidance groove, not shown, generally centrally of the track way 1 so as to locate guidance conductors 4 and 6 within the space defined by the guidance groove. The guidance conductor 4 including a guide path 4a and a lead wire 4b is connected to a high frequency current source 5, the guide path 4a being laid within the guidance groove formed along the main way 2. The guidance conductor 6 including a guide path 6a and a lead wire 6b is also connected to a high frequency current source 7, the guide path 6a being laid within the guidance grooves formed along both the main way 2 and the branch ways 3 and 3. The lead wires 4b and 6b, which are often suspended from a ceiling or supported at a wall, are employed for coupling the guidance paths 4a and 6a to the respective current sources 5 and 7, and the lead wires 4b and 6b do not serve as a guidance means for a driverless vehicle 27 described hereinafter since they are not laid on the track way 1. The high frequency current sources 5 and 7 have different frequencies f1 and f2, respectively with each other, so that the guidance couductors 4 and 5 are energized to allow different high frequency currents to flow independently relative to each other. A driverless vehicle which rides upon the surface of the track way 1 is guided to move along the track way 1 by detecting, with a detector mounted on the vehicle, either the electromagnetic field generated by the guidance conductor 4, or that generated by the guidance conductor 6. When it is required to direct the driverless vehicle to take one of the branch ways 3 and 3 from the main way 2, the detector is controlled to receive only the high frequency f2 which acts on the branch ways 3 and 3. While on the other hand, the change of the direction of the vehicle from the branch ways 3 and 3 to the main way 2 is similarly effected by rendering the receptive condition of the detector responsive to the high frequency f1 instead of the high frequency f2. It is readily understood here from the principle of operation that if one of the lead wires 4b and 4b of the guidance conductor 4 was laid for returning it to the current source 5 by way of the same guidance groove where the guide path 4a is laid, the high frequency induction fields generated by the guide path 4a and the lead wire 4b will interfere with each other thereby resulting in an incorrect guidance for the driverless vehicle. The same interference may also be true in connection with the guidance conductor 6, if one of the lead wires 6b and 6b was laid within the same guidance groove where the guide path 6a is laid. Therefore, it has been a requisite for the lead wires 4b and 6b to be returned to the respective high frequency current sources 5 and 7 by way of different courses from the guidance grooves formed in the track way 1, such as for example by routing it via the ceiling above the track way 1 or the nearby wall where it is not susceptible to electromagnetic interference. This necessarily leads to a complicate laying work of the lead wires of the guidance conductor and, in addition, leads to an expensive cost of materials and construction work. In the case of track ways where a plurality of branch ways are employed, the above disadvantages accompanied by the conventional guidance conductors have been extensively enhanced. Moreover, it has also been a problem in that so many high frequency current sources are required to be implemented in proportion with the number of branch ways.